A variety of cellulosic polymers are known to be useful in the preparation of dosage forms. They are often combined with other polymers and used as coatings or shells for dosage forms. For example, WO 01/32150 discloses an edible, hardenable coating composition containing microcrystalline cellulose, carrageenan, and at least one of a strengthening polymer, a plasticizer, a surface active agent or a combination thereof. The composition provides a prompt, i.e., immediate, release coating for solid dosage forms and is applied by spray coating.
WO 00/40223 relates to a composition comprising hydroxypropylcellulose and at least one anionic polymer such as carboxymethyl ether salts of cellulose, methacrylic acid polymers and copolymers, carboxyvinyl polymers and copolymers, alginic acid salts, pectinic acid salts, pectic acid salts, carrageenan, agar and carboxylic acid salts of polysaccharides. The ratio of hydroxypropylcellulose to anionic polymer is from 1:20 to 20:1. The composition is used as an aqueous solution to coat substrates.
U.S. Pat. No. 6,358,525 B1 discloses a pharmaceutical composition containing a medicament and a blend of two components. The first component is hydroxypropylcellulose and the second component is at least one other polymer selected from a group that includes carrageenan, agar, and gellan gum. The pharmaceutical composition is formed into a tablet that may be coated with a conventional coating material.
U.S. Pat. No. 6,245,356 B1 relates to a sustained release, oral, solid dosage form comprising agglomerated particles of a therapeutically active medicament in amorphous form, a gelling agent, an ionizable gel strength enhancing agent and an inert diluent. The gelling agent preferably comprises xanthan gum and locust bean gum, but may alternatively comprise alginates, carrageenan, pectin, and other compounds. The ionizable gel strength enhancing agent may be a monovalent or multivalent metal cation. The active medicament in amorphous form, gelling agent, ionizable gel strength enhancing agent and an inert diluent are mixed or granulated together and formed into a tablet.
Known compositions comprising water soluble polymers are often difficult to use, for example in coating operations, because their viscosity becomes too high, especially with increasing polymer concentrations, or increasing polymer molecular weight. Spraying and molding processes can be particularly difficult. Accordingly, dilute solutions must be used, resulting in lengthy processing times to build up adequate thickness.
Applicants have now discovered that a composition comprising a combination of a high molecular weight, water soluble polymer having a cloud point from about 20 to about 90° C. and one or more carrageenans, in certain embodiments with gellan gum and in other embodiments with both gellan gum and a lubricant, may be used as a component of a dosage form, for example as the shell of a dosage form containing active ingredient in an underlying core. The high molecular weight, water soluble polymer and the carrageenan can be dispersed in water, along with other ingredients, at a temperature above the cloud point of the high molecular weight, water soluble polymer, leaving the high molecular weight, water soluble polymer undissolved and the viscosity of the dispersion manageable. The dispersion flows easily, and sets quickly and strongly at a relatively high temperature due to the presence of the carrageenan. Cores containing active ingredient can advantageously be coated with this composition, preferably by molding, to prepare dosage forms that provide a burst release of the active ingredient.